n = True
while n:
    i = int(input("输入成绩："))
    if 90 <= i <= 100:
        print("A")
    elif 60 <= i < 90:
        print("B")
    elif 0 <= i < 60:
        print("C")

s = input("输入:")
def f(x):
    if x == -1: 
        return ''
    else:      
        return s[x] + f(x-1)
print (f(len(s)- 1))
